Photographing film recording apparatus comprising a cathode ray tube having a face plate with inner electron targets correspondingly connected to outer electroluminescent elements



Jan. 30, 1968 w. A. MILLER 3,366,817

PHOTOGRAPHING FILM RECORDING APPARATUS COMPRISING A CATHODE RAY TUBE HAVING A FACE PLATE WITH INNER ELECTRON TARGETS CORRESPONDINGLY CONNECTED TO OUTER ELECTROLUMINESCENT ELEMENTS Filed Aug. :5, 1965 2 Sheets-Sheet 1 FIG. I

. VERT.

sumac DEFL SOURCE I0 f II POTENTIAL (PRIOR ART) v INVENTOR. WILLIAM A. MILLER ATTORNEYS Jan. 30,1968

w. A. MILLER I 3,366,817 PHOTOGHAPHING FILM RECORDING APPARATUS COMPRISING A CATHODE RAY E PLATE WITH INNER ELECTRON TARGETS CORRESPONDINGLY CONNECTED TO OUTER TUBE HAVING. A FAC ELECTROLUMINESCENT ELEMENTS 2 Sheets-Sheet z Filed Aug. 5, 1965 FIG. 5

INVENTOR. WILLIAM A. MILLER v BY I 5 ATTORNEYS United States ABSTRACT OF THE DISCLOSURE A cathode ray tube useful for recording purposes in which the electron stream bombards targets on one side of a face plate to which are electrically connected discrete electroluminescent display elements which are located on the other side of the face plate. A conductive coating is provided to dissipate the electrical charge on the face plate.

This invention relates to cathode ray tubes and more particularly to a cathode ray tube having particular utility for photographic recording of the images displayed thereon.

Many situations arise where it is necessary to make a permanent photographic record of data, either in pictorial or bit form, which is displayed as an image on a light emitting coating, such as a phosphor coating, visible through the face plate of a cathode ray tube. This recording, that is the taking of a picture of the image displayed on the tube, is desirably accomplished as rapidly as possible so that short persistence high definition phosphors may be used for the tube to increase the resolution of the image displayed. In making photographs of a cathode ray tube display, a problem is also encountered due to the distortion and diffusion of the light through the glass face plate. It is of course desirable to reduce this distortion to a minimum so that the displayed image can be photographed with the greatest fidelity.

In the present state of the art making photographic records of images displayed on cathode ray tubes generally requires the use of an optical lens between the face plate of the tube and the photographic recording medium. Unlike the normal photographic objective lens used with cameras, which are relatively simple to construct, lenses for use with cathode ray tubes for the purpose of making photographic records generally must satisfy rather stringent requirements. These include the capability of providing a magnification close to unity with high photographic speed and the production of a flat objective plane as well as a fiat image plane to reduce distortion. Consequently, these lenses are expensive to construct and difiicult to focus for optimum performance.

In accordance with the present invention, a novel cathode ray tube is provided which has particular utility for making photographic recordings of the images displayed thereon. This tube includes a predetermined pattern of elements of light emitting material such as phosphor, placed on the outside of a face plate sealing off the end of the tube. Each of the elements is electrically connected to one or more selected conductors of an array, or matrix, of conductors which extend through the face plate and each selected conductor or group of conductors has a conductive target connected thereto. The targets are all located within the evacuated portion of the tube to receive the electrons in the stream or beam, emitted by the cathode of the tube. Upon a target receiving such elecate 3,366,817 Patented Jan. 30, 1968 trons the element connected thereto is energized to emit light.

Since the light emitting elements are located on the outside of the face plate, the photographic film recording medium can be placed into very close proximity thereto. Whereas in a conventional cathode ray tube photographic setup the film is spaced from the light emitting material of the tube by the thickness of the face plate and the optical path of the lens system, in the present invention the only separation is the thickness of one or more coatings placed over the outer surface of the light emitting elements. Since the coatings can be made relatively thin, there is little light lost in the transmission path between the elements and the film, permitting the use of lower speed films, and there is essentially no distortion. Also, by using the targets connected directly to the light emitting elements, a substantially uniform brightness distribution pattern is achieved for each element rather than the non-uniform brightness distribution pattern usually obtained in a conventional tube with phosphors distributed over the face plate of a tube.

It is therefore an object of the present invention to provide a cathode ray tube for use in the photographic recording of displayed images.

Another object is to provide a cathode ray tube in which the light emitting elements are located on the outside of the face plate of the tube.

A further object is to provide a tube for photographically recording images displayed thereon in which the photographic film may be placed in close proximity to the light emitting elements.

An additional object is to provide a cathode ray tube for use in a film recording system which obviates the need for an optical lens.

Yet another object is to provide a cathode ray tube whose light emitting elements are energized by electrons impinging on a conductive target connected thereto.

Still a further object is to provide a cathode ray tube in which the light emitting elements have a substantially uniform brightness distribution pattern.

Other objects and advantages of the present invention will become more apparent upon reference to the following specification and annexed drawings in which:

FIGURE 1 is a side elevational view of the cathode ray tube of the present invention taken partially in section and showing in schematic block diagram form the circuitry for controlling the tube;

FIGURES 2A, 2B and 20 respectively show side, front and rear views of a portion of the face plate of the tube in enlarged form;

FIGURES 3A and 3B respectively show the brightness distribution curves obtainable with cathode ray tubes of the prior art and of the present invention;

FIGURE 4 is a front view of one form of the data display pattern producible with the tubes of the present invention;

FIGURE 5 shows another type of data display; and

FIGURE 6 shows another arrangement for the wire matrix array and targets.

Referring to FIGS. 1 and 2A through 2C, the tube 10 has an envelope 11 of any desired shape which is made of any suitable material, such as glass. A cathode 13 is provided at one end of the tube for emitting electrons. Cathode 13 is of any suitable conventional construction well known to those skilled in the art, the details of which are not important to the present invention. Consequently, the cathode is shown only in schematic form.

The electrons emitted by cathode 13 in a beam or stream are controlled by a Video data source 14 whose output is suitably connected to a grid electrode 15. The video data source may be any suitable source of video signals either in continuous or bit form. Grid electrode 15 is also of conventional construction. It is sufficient to say that the electrons emitted from cathode 13 are intensity modulated by the grid 15 under the control of the video data source 14.

The tube is also preferably provided with a focus control electrode 17 of any suitable type operating from a source of focus control current or voltage 18. As is well known, adjustment of the source 18 current or voltage focuses the electron beam to a desired diameter within the design limits of the tube.

Also located adjacent to the focus control electrode 17 are a pair of horizontal deflecting plates 20 and 20a and a pair of vertical deflecting plates 21 and 21a. One horizontal deflecting plate 20a and one vertical deflecting plate 21a are connected to a suitable source of reference potential 23 (not shown). The other horizontal deflecting plate 20 is connected to a source of horizontal deflection signals 22 while the other vertical deflection plate 21 is connected to a source of vertical deflection signals 23. The sources of horizontal and vertical deflection signals 22 and 23 are of any suitable conventional type for producing either a continuous scan both horizontally and vertically or for positioning the electron stream emitted by cathode 13 at any particular point on the face of cathode ray tube. Such circuits are also conventional in the art. While an electrostatic type of deflection system is illustratively shown, it should be understood that a suitable electromagnetic system may be utilized instead.

An accelerating electrode 24 is also provided which is connected to a source of accelerating potential 24a. These are commonly called the second anode and second anode potential. As should be understood, all of the elements of the tube described so far are conventional in the art and any suitable tube structure may be utilized.

A face plate 25, which is preferably formed separately, is bonded to the end of the envelope 11 opposite the cathode 13 by a seal 27 completely around the face plate and envelope where they meet. The face plate 25 is preferably made of glass, or glass frit, and, if the tube 11 is also made of glass, any suitable glass sealing technique may be utilized. Face plate 25 seals off the envelope 11 so that it may be evacuated.

The face plate has embedded therein an array, or matrix, of conductive wires 30. The individual wires of the matrix are shown in the preferred embodiment of the invention of FIGS. 1-2, generally parallel to each other and they are preferably uniformly spaced, although this is not absolutely necessary. Each wire 30 is completely surrounded by the glass material of the face plate so that it is not necessary to provide any additional insulation for the wires.

All of the wires 30 of the array extend completely through both sides of the face plate 25 so that a portion of each wire is available on both the back of the face plate, that is that portion of the face plate which is inside the tube and subject to bombardment by the electron stream, and the front of the plate, this is, that portion of the face plate which is exposed to the viewer.

A plurality of separated targets 32 of suitable conductive material, such as copper for example, are laid down in a predetermined pattern on the back of the face plate. While the targets 32 are illustratively shown as being circular, they may have any desired shape. Each target 32 is electrically and selectively connected to one or a plurality of the wires 30. The targets 32 can either be electrodeposited or photo-etched onto the back of the face plate or placed thereon by any other suitable technique as is conventional in the art. As can be seen in FIGURES 2A through 2C, not all of the wires 30 are connected to the targets 32 in accordance with the target pattern laid down on the back of the face plate.

The outside of face plate 25 has a plurality of light emitting elements 35 placed thereon. Each element is formed by a quantity of a material which emits light upon being energized by an electric potential. Suitable materials for the elements 35 are those of the phosphor and electroluminescent type, including voltage sensitive phosphors, a multitude of which are available in the art to produce a broad range of colors and persistences. The areas between elements which do not have light emitting material deposited thereon are preferably made opaque, as indicated by the portions 34 (FIG. 2A) so that there is no diffusion of light emitted by the elements, that is, the emitted light is confined to the area of the element itself.

Each of the elements 35 is electrically connected by one or more wires 30 to the corresponding target 32 connected to the same wires. In the preferred embodiment of the invention being described in FIGS. 1 and 2, the pattern of element 35 is juxtapositioned on top of the pattern of targets 32 and is in registration therewith. As shown, each element 35 is electrically connected only to those wires 30 which are connected to the corresponding target 32 which is used to control energization of the element. By this it is meant that there is a 1:1 ratio between targets 32 and elements 35 so that an element 35 does not overlap the wires 30 connecting two of the targets 32, or vice versa. Therefore, an individual target 32 controls an individual light emitting element 35. Such 1:1 correspondence is preferred but is not absolutely necessary so that one target can control a plurality of elements, or vice versa.

A thin coating 36 of a transparent material having electrical conductivity properties is deposited over the front of the face plate to serve as a sink (return) for the electrons. The coating 36 is connected to a source of reference potential, such as ground 37, or any other value of potential. The majority of the material of the coating 36 preferably is located in the spaces between the elements 35. Since the electrically conductive material of coating 36 electrically contacts all of the elements and all of the wires 30 which are not connected to elements, a return path is provided for the electrons bombarding the back of the face plate. If desired, the conductive material can be coated over the elements 35 to assure a good return path. This coating over the elements 35 need be only very thin and since the coating material is transparent, the light emitted by the elements can pass therethrough very easily. The coating material may be of any suitable type, for example, semi-transparent evaporated metal of suitable characteristics, or tin chloride or oxide prepared from chemicals by well-known techniques.

The complete phosphor element and transparent conductive coating are in turn covered by a protective coating 38 also of transparent material which is also preferably very thin. The coating 38 may be made identically or similarly to coating 36.

As shown in FIGURE 1, a photographic film 40 is placed adjacent the transparent protective coating 38 on the face plate. The photographic film may be supplied from a suitable feed mechanism (not shown) and any suitable take-up mechanism, also may be provided. These are not shown since many conventional systems are available for performing the feed and take-up functions. Some of these are energized by the vertical deflection system to move the film one frame after a complete frame has been displaced on the tube.

It should be noted that the film 40 is in extremely close proximity to the light emitting elements 35 on the face plate, being separated only by the thickness of the protective coating 38 and the conductive coating 36. Both of these are extremely thin as compared to the thickness of the face plate of a conventional cathode ray tube.

In operation, electrons emitted by the cathode 13 are controlled in intensity by the grid 15, focussed by electrode 17 and positioned onto the back of the face plate 25 by the deflecting electrodes 20 and 21 to impinge upon selected ones of the targets 32. Each time the electron stream impinges upon a target 32, the electrons in the stream are conveyed through the wires 30 connected to the target 32 to the corresponding connected light emitting element 35. These electrons increase the electric potential of element 35 which excites the emitting material causing it to produce light. To state it another way, the electrons in the stream impinging upon a target produce a charge thereon which is of a magnitude suflicient to excite the light emitting material. The charge is leaked off through the light emitting material and the coating 36 to the source of reference potential.

The light emitted by each element 35 is of a predetermined wavelength in accordance with the characteristics of the selected light emitting material and of an intensity corresponding to the density of the electron stream, as controlled by grid 15 and the video data source 14. The transparent conductive coating 36 as well as the transparent protective coating 38 do not hinder the transmission of the light from the phosphor element 35 and therefore the emitted light directly exposes the corresponding portion of the film 40 which is located adjacent coating 38. As should be clear, no lens system is needed between the face plate and the film and distortion is limited only to the thickness of coatings 36 and 38. This distortion is relatively small since the film can be physically positioned very close to elements 35.

FIGURE 3A shows the relative brightness distribution curve for a conventional cathode ray tube in which phosphor is deposited more or less uniformly on the faceplate and the electron beam impinges directly upon the phosphor. The ordinate (I) represents intensity and the abscissa (D) represents distance from the center of the electron stream. As can be seen, the curve for a light emitting element, which is formed by a number of grains of phosphor, does not give a uniform distribution pattern and the light output drops off rather sharply from the center of the stream diminishing to almost zero at the periphery of the diameter of the electron stream. FIG. 3B shows the more uniform brightness distribution pattern for a light emitting element 35- of the present invention. This occurs due to the fact that the electron stream striking any portion of a target 32 causes the entire element 35 connected to that target to receive substantially equal amounts of electron beam current.

With the face plate arrangement of FIG. 2, where the elements 35 are separated, the elements do not produce fringing when excited to produce light. Fringing is herein defined as the mutual excitation of adjacent particles of the light emissive material by one another or, excitation by the peripheral portion of the electron beam which is of lower current density than the center of the beam. As should be evident, each light emitting element 35 is separated from all other elements both physically and electrically so there can be no fringing. The provision of the opaque areas 34 also more sharply define and contain the light emitting areas.

FIGURE 4 shows one form of the invention having a display pattern of elements 35 and targets 32 suitable for reproducing binary type data. Here, the elements 35 are arranged in a column and row array with a corresponding pattern of targets 32 (not shown) located directly behind on the other side of the face plate 25. In this embodiment the parallel wire matrix arrangement of FIGS. 1-2 is also preferably used. By suitably positioning the electron beam through the use of the deflection circuitry (FIG. 1) and controlling the video source 14, selected elements 35 are energized to emit light. Energization of an element corresponds to a 1 bit (or 0 bit) and nonenergization to a 0 bit (or 1 bit). For each frame scan, that is the movement of the beam past each element 35 of the display pattern, a predetermined pattern of elements are energized to produce data in accordance with the data from source 14. This is permanently recorded on the film (not shown).

In the embodiment of the invention shown in FIGURE 4, the spacing between targets 32 is preferably made somewhat greater than the diameter of the electron beam. Therefore, the electron beam can be selectively positioned to energize only one element-35 at any one time. As the beam is moved between successive targets 32 the video data source is preferably provided with a blanking signal from a blanking source 50 which blocks the electron beam 13 from reaching the face plate. This action is also conventional in the art.

In one form of cathode ray tube constructed in accordance with the embodiment shown in FIG. 4, a face plate is used having a density of wires 30 of about 125,-

000 per square inch. These wires are laid substantially parallel to each other and are non-contacting. The targets 32 and the light emitting elements 35 are deposited on the back and front of the face plate respectively with a spacing of about .018 inch from center to center and diameters of approximately .008 inch. Using this arrangement approximately one to five wires are connected to each target 32 and the corresponding connected element 35. Since the electron stream diameter, spot size, can be readily focused to between .0009 to .0018 of an inch in diameter the spot size can be made to selectively impinge upon only one target 32 at a time.

As the electron stream moves between targets 32 and if no blanking signal is utilized, impingement of the electron stream upon the wires 30 which are not connected to a target will not produce any light emission and these elements are returned to the source of reference potential through the conductive coating 36. Therefore, the tube provides a high degree of resolution in the sense that only one selected light emitting element 35 is energized at any one time by the stream.

It should be understood that an element 35 is energiz ed to produce light no matter what area of the corresponding target 32 is struck by the electron stream. By this it is meant that the electron stream does not have to hit the center of a conductive target 32 since impingement of the electron stream onto any area of a target 32 conveys the electrons to the corresponding electrically connected element 35 through the connected wires 30.

In another embodiment of the invention half tone printing may be produced by spacing the targets and light emitting elements closer together. In this case, for example, targets and elements .001 inch in diameter can be placed on a .002 inch center to center spacing. The spot size of the beam is focused so as to energize only one element at a time as it is continuously scanned over the face plate. Blanking is provided only during line, field and frame retrace. Such an arrangement provides a high degree of resolution which makes the cathode ray tube useful for direct print-out of computer information onto photographic film. Of course, the direct optical display also may be used.

While the embodiment of the tube shown in FIGURE 4 is designed particularly so that only one element 35 is energized at any one time by the electron beam, it should be understood that the invention is not to be limited to this arrangement. For example, the spacing between targets 32 may be arranged so that the electron beam strikes several targets to energize several e.'e ments at the same time.

FIGURE 5 shows another embodiment of the invention for producing an alpha numeric display. Here, any desired register of light emitting elements 55, shaped in the form of alphabetical or numerical characters, or combinations thereof, is placed on the front of the face plate 25. Each element 55 in the form of a number or a letter corresponds to one of the elements 25 of FIGS. 1 and 2. Using the target-element arrangement of FIGS. 1 and 2A-2C, the back of the face plate is provided With a conductive target (not shown) for each element 55. Each target has the same shape as the corresponding electrically connected element 55 and the matrix of parallel wires 30 (not shown) run therebetween. As the electron beam strikes a portion of any one target, the entire element connected thereto emits light. The details of the tube of FIG. 5, such as the semiconductive and protective coatings, are not shown.

As explained above, the tube of FIGURE may be provided with the parallel wire grid array of FIGURES 1 and 2. FIGURE 6 shows an alternate target array in which a single target 62 of a desired shape, such as circular, is provided for each light emitting element and the wires 60 diverge therefrom to all areas of an eement 65. This type of target is easier to lay down on the back of the face plate in a predetermined pattern and simplifies the problems in deflecting the electron beam to the proper target. The use of the diverging wire arrangement permits the elements 65 to be of any desired shape, such as alpha-numeric, even though the targets are of another shape.

The cathode ray tubes of the present invention have several advantages in addition to those described above. For example, when used for photographic purposes in which the film is essentially in contact with the light emitting elements, the tube can be operated with low cathode current and low second anode potential. This allows both a small electron beam diameter, high deflection sensitivity, and long tube life. Loss of emission from the elements 35 can be corrected by removing the face plate 2.5 entirely and replacing it or by redepositing new light emitting material. Both of these processes can be carried out without discharging the remaining portions of the tube.

It also should be noted that the deposition pattern of light emitting elements on the outer face of the face plate can be accomplished at will and therefore when a high wire density grid is used the pattern can be readily changed. Also, as explained above, the tube of the present invention can be used for direct viewing and/or purposes other than photographic reproduction.

While certain present preferred embodiments of the invention have been illustrated and described, it is to be understood the invention may be otherwise embodied within the spirit thereof, within the scope of the accompanying claims.

What is claimed is:

1. In combination with a cathode ray tube the improvement comprising:

a face plate of insulating material,

a plurality of conductive wires embedded in said face plate at least some of which are exposed for electrical connection on both sides of said face plate,

a plurality of targets of electrically conductive material located on the side of the face plate adapted for receiving an electric charge from the electron stream of the cathode ray tube, each target being electrically connected to at least a respective one or more of said wires,

a plurality of elements each formed of a material capable of emitting light in response to receiving electrons, each said element located on the other side of said face plate and being electrically connected to at least one of the wires connected to a respective target, impingement of electrons onto a said target energizing the material of the corresponding connected element to emit light,

and a coating of at least partially conductive material in electrical contact with said elements adapted for connection to a source of reference potential to provide a return for said electric charge.

2. Apparatus as set forth in claim 1 wherein a coating of transparent material is placed over said conductive material and said elements.

3. Apparatus as set forth in claim 1 wherein said elements have a discrete physical size and shape.

4. Apparatus as set forth in claim 3 wherein the targets and elements are of the same general shape and s1ze.

5. Apparatus as set forth in claim 3 wherein the targets and elements are of different shapes.

6. A cathode ray tube as set forth in claim 1 wherein said elements are in the shape of alpha-numeric characters and a respective single target is connected to control the energization of a respective element.

7. A cathode ray tube as set forth in claim 1 wherein said elements all have substantially the same shape and a respective single target is connected to control the energization of a respective element.

8. Apparatus as set forth in claim 1 wherein said coating is also in electrical contact with wires unconnected to elements.

References Cited UNITED STATES PATENTS 2,015,570 9/1935 Sabbah et al. 346ll0 2,267,827 12/1941 Hubbard 31392 3,195,219 7/1965 Woodcock et al. 2925.18

JAMES W. LAWRENCE, Primary Examiner.

V. LAFRANCHI, Assistant Examiner. 

